You kind of have to look at your kids and see if they are ready as well, and I don't mean if they will feed her and walk her (you've already said that would be your job). My kids desperately want a dog, but at 6 and 3 years old they aren't at the age where they notice their toys laying on the floor, a video game controller left out, a pile of books sitting at the end of the couch... but a dog would!
A puppy of any breed is going to chew and chew and chew for at least the first year of it's life, not only would a puppy in our house chew every lego, book, and frizbee it found on the ground, but it if swallowed said lego we would end up at the vet with a very expensive bill on our hands.
Also, how small is your 4 year old? My 3 year old is in the 5th% and would be knocked right over by any rambunctious puppy, not a good start to a relationship.
I'm also already up to my ears in sweeping, vacuuming, and mopping our house with two kids who spill, drip, and crumble... I know that a dog spilling it's water (or a kid accidentally spilling the dog's water), fur on the carpet, slobber on the bed... would drive me up the wall, just another mess to clean. From previous experience with dogs (we owned two before having kids) I know that having patience with my children is easier for me than having patience with a dog.
All this said, no, I personally would not jump on this offer, but that's my assessment of MY household and MY children. Take a look at your family and see if you are ALL ready for a dog, even if you yourself are planning on being it's primary caregiver it WILL be the family dog.